Metals and non-metals

One basis of classification of the elements groups them into metals and non-metals. It is with the metals that we shall concern ourselves, considering the group as a whole.

The first metals which were used by primitive man were those that are found free in nature to the greatest extent. These are gold, silver, and copper. Tin entered the metal picture when someone discovered, probably accidentally, that if it was mixed with copper the resulting substance was harder. So there came into being the alloy that we call bronze, a material which was so important in the ancient world that its name is given to one of the cultural stages in human development. The Bronze Age began in Egypt around 3,000 before our era and in Europe some 500 or 1,000 years later.

Since almost no iron exists free in nature, it undoubtedly came into general use somewhat later than those just mentioned. However, the Egyptians and Assyrians made some use of iron a number of centuries before our era. As soon as methods were developed for separating iron from its ores in reasonably large quantities and at fairly low cost, it ceased to be classed as a precious material and began its career as the world’s most valuable metal from the standpoint of actual use.

Copper was one of the first metals used by man; the reason is that it is found free in nature to a comparatively large extent.

It is only since man has learned how to obtain and use metals and their alloys that he has been able to adapt his environment to his needs and desires. The present age is, in fact, the Age of Metals and it is important that we should have some acquaintance with these useful substances.

In the ancient times, gold, silver, copper, tin, iron, lead and mercury were known as “The Seven Metals”.

One other metal, zinc, has also been known in its role as one of the constituents of the alloy brass. Almost no metals other than these seven or eight were known until the eighteenth century and many that we use today, not until the nineteenth.

Metals are mostly solids at ordinary temperature and have comparatively high melting points with the exception of mercury. They are for the most part good conductors of heat and electricity, and silver is the best in these respects. They can be drawn into fine wires and hammered into thin sheets, characteristics that are called ductility and malleability, respectively. An ounce of gold can be drawn into a wire almost 50 miles long or hammered into a sheet that has an area of between 175 and 200 square feet.

In considering the chemical properties of metals, the first point which must be mentioned is that they vary widely in degree of chemical activity: some are enormously active and others very inert. In general, metals are chemically combined with one or more other elements and the compounds are known as ores.

Alloys are usually prepared, simply by melting two or more metals together and then this liquid mixture is allowed to cool and solidify. If no chemical reaction occurs between or among the constituents, the resulting alloy is a simple mixture. In some cases there is a definite reaction and the resulting alloy is a chemical compound. In a third type the degree of combination of the metals is such that the product can be described best by calling it a solid solution.

The enormous importance of alloys lies in the fact that by combining metals in this fashion almost any desired set of properties can be attain ed.